Researchers combined X-ray surveys and supercomputer simulations to track 12 billion years of cosmic black-hole growth.
Their findings reveal that
Mechanisms of Supermassive Black Hole Growth
“Supermassive black holes in galaxy centers have millions-to-billions of times the mass of the Sun,” said Fan Zou, a graduate student at Penn State and first author of the papers. “How do they become such monsters? This is a question that astronomers have been studying for decades, but it has been difficult to track all the ways black holes can grow reliably.”
Supermassive black holes grow through a combination of two main channels. They consume cold gas from their host galaxy — a process called accretion — and they can merge with other supermassive black holes when galaxies collide.
Data Sources and Accretion Measurement
“During the process of consuming gas from their hosting galaxies, black holes radiate strong X-rays, and this is the key to tracking their growth by accretion,” said W. Niel Brandt, Eberly Family Chair Professor of Astronomy and Astrophysics and professor of physics at Penn State and a leader of the research team. “We measured the accretion-driven growth using X-ray sky survey data accumulated over more than 20 years from three of the most powerful X-ray facilities ever launched into space.”
The research team used complementary data from
“All of the galaxies and black holes in our sample are very well characterized at multiple wavelengths, with superb measurements in the infrared, optical, ultraviolet, and X-ray bands,” Zou said. “This allows for robust conclusions, and the data show that, at all cosmic epochs, more massive galaxies grew their black holes by accretion faster. With the quality of the data, we were able to quantify this important phenomenon much better than in past works.”
Mergers and Simulated Growth
The second way that supermassive black holes grow is through mergers, where two supermassive black holes collide and merge together to form a single, even more massive, black hole. To track growth by mergers, the team used IllustrisTNG, a set of supercomputer simulations that model galaxy formation, evolution, and merging from shortly after the DOI: 10.3847/1538-4357/ad27cc
In addition to Zou and Brandt, the research team includes Zhibo Yu, graduate student at Penn State; Hyungsuk Tak, assistant professor of statistics and of astronomy and astrophysics at Penn State; Elena Gallo at the University of Michigan; Bin Luo at Nanjing University in China; Qingling Ni at the Max Planck Institute for Extraterrestrial Physics in Germany; Yongquan Xue at the University of Science and Technology of China; and Guang Yang at the University of Groningen in the Netherlands.
Funding from the U.S. National Science Foundation, the Chandra X-ray Center, and Penn State supported this work. The work was also made possible by the sharing of the